The medieval Asen's fortress is situated 3 km south of the town of Asenovgrad town, on a high rocky ridge on the left bank of the Asenitsa River. The earliest archaeological findings dated back to the 4-5th century BC, when Thracians valued the inaccessibility of the terrain and built a fortification here. The area of the fortress was inhabited as well as in the Roman and the Early Byzantine era.

The Asen's fortress was first mentioned in the Statute of the Bachkovo Monastery, where it was called "the fortified village of Petrich". In the Middle Ages the Asen's fortress underwent several construction periods. It was considerably renovated in the 13th century (more precisely 1231) during the rule of Bulgarian tsar Ivan Asen II. The eight-line wall inscription in Bulgarian language above the entrance of the fortress testifies for the event: "In the year 6739/1231/, indict 4, Tsar Asen, enthroned by God, ruling over Bulgarians, Greeks and other countries put Aleksi Sevasta and built this town."
In the new time, this inscription became a reason the Citadel Petrich to be named Asen’s, upon the name of Ivan Asen II, and the nearby town was renamed from Stanimaka in Asenovgrad. The great building work of the Medieval time is supported by archaeological researches - the foundations of the fortress walls, a feudal castle, 30 rooms and 3 reservoirs have been excavated. But the biggest attraction of the fortress, remained to the present days, is the Church of the Holy Mother of God of Petrich /13th century /. It is a two-storey cross-domed single-naved building with a wide narthex and a large rectangular tower. The architectural grace, decorative plastic decoration of the southern façade and unique mural paintings from the 14th preserved partly in the naos (Greek for temple), assigned the temple to the best examples of Medieval Bulgarian church construction in our land.
Taken by the Byzantines after Ivan Asen II's death, the fortress was once again in Bulgarian hands at the time of Ivan Alexander in 1344 only to be conquered and almost destroyed by the Ottomans during their rule of Bulgaria. Then, as a result, it lost its strategic meaning of a frontier fortress.
The site is served by a tour guide.